1. Field of the Invention
This invention relates to the field of magnetic alloys. More specifically, this invention comprises a method for producing cobalt-platinum permanent magnetic alloys with improved magnetic properties.
2. Description of the Related Art
Cobalt-Platinum (“CoPt”) alloys are the preferred metal alloys in various instruments that require hard magnetic materials. These magnetic alloys are particularly useful in intravascular navigation and drug delivery applications where magnetic CoPt wires are used to guide catheters through a patient's veins or arteries. These applications often require a magnetic component that has high coercivity (iHc) but low energy product (BH)max, where H is the external magnetic field strength and B is the magnetic induction.
CoPt alloys having the aforementioned properties are generally processed in one of two ways. In one process, the CoPt alloy is heated to a temperature of 950-1000 degrees C. for 3 hours in a protective atmosphere to prevent oxidation. The alloy is then cooled to approximately room temperature before being transferred to a salt bath maintained at 660 degrees C. for one and half hours. The alloy is then either quenched or cooled slowly. The typical magnetic properties for CoPt alloys prepared using this method include a remanence (Br) of approximately 6.4 kGs, a coercivity (iHc) of approximately 4.8 kOe, an energy product ((BH)max) of approximately 9.2 MGOe.
In the second method, the CoPt alloy is heated at 900-1000 degrees C. for 3 hours in a protective atmosphere. The alloy is then cooled to room temperature. After being cooled to room temperature, the alloy is “aged” at a temperature of 500-700 degrees C. for 5-20 hours. The alloy is finally either quenched or cooled slowly. The typical magnetic properties for CoPt alloys prepared using this method are Br=6.3 kGs, iHc=4.95 kOe, and (BH)max=9.0 MGOe.
Conventional processing methods are not perfect and the magnetic alloys produced using conventional processing methods may also be improved. Those skilled in the art know that controlling the cooling rate of CoPt from a temperature of 1000 degrees C. to room temperature is difficult to accomplish and time consuming. The use of a salt bath also results in the production of hazardous vapors. Accordingly, it would be desirable to provide a new processing method for producing CoPt alloys with improved properties while avoiding many of the problems associated with conventional processing techniques.